BENDIN' BACTERIUM
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Biology and physics professor Ozgur Sahin is conducting research on how a type of bacteria spore responds to environmental changes—and how the germs’ responses could be harnessed to generate electricity.

If biology and physics professor Ozgur Sahin’s research in bacteria spores proves fruitful, the world could soon be running on electricity produced by the tiny movements of microbes.

While studying the survival mechanisms of Bacillus subtilis—a type of spore commonly found in soil—Sahin noticed that the typically rigid microbe was actually able to undergo great expansion and contraction as the humidity of the surrounding environment changed.

During periods of relatively high humidity, water enters the spores and their structures expand.

“Even a small amount of water is sufficient to make them move,” Sahin said. This is remarkable because “usually a material stretching so much would be damaged.”

He decided to find a way to take advantage of this anomaly. In a Jan. 26 paper published in the science journal Nature, Sahin, along with Loyola University professor Adam Dirks, Harvard math professor L. Mahadevan, and Postdoctoral Research Scientist at Columbia Xi Chen, described how the bacteria could be used to create tiny biological mechanisms or generate electricity.

The fundamental idea behind this technology is beautifully simple. Sahin’s lab proposed coating a flexible material such as latex with the bacteria to observe its movement. As the individual spores change shape in response to the humidity, the latex material would start bending too. This could then be connected to a turbine, which would generate electricity from the motion.

In the Nature article, the authors noted that the bacteria’s mechanical response was more than twice as powerful as similar synthetic materials, and that some mutant forms of the bacteria have as much as 100 times the energy density.

“You cannot imagine how excited I was when we found out that materials from nature are much more powerful than any synthetic material,” Chen, who also works in Sahin’s lab, said.

Sahin’s lab on the ninth floor of the Northwest Corner Building has a humidity-controlled room specially designed for watching the bacteria bend on a latex sheet.

“If we can make evaporating moisture go into spores, we can harvest energy directly from the bacteria,” he said.

Sahin said that the technology could potentially be even more effective than current forms of renewable energy.

Compared with solar and wind energy, which are dependant on certain weather conditions, harvesting energy from bacteria can happen anytime regardless of the weather. Hydroelectric plants also cause more fresh water to evaporate from the reservoirs created by the dams—something a bacteria-based process would mitigate.

“We need to develop energy technologies that are less dangerous to people and the planet than the current mix of technologies we rely on,” Steve Cohen, the executive and chief operating officer of the Earth Institute, said in an email. “We need creative scientists like Professor Sahin to develop innovative methods of generating the energy that is so central to our way of life.”

Still, Sahin said that there’s still much more research to do to convert the bacteria-coated-latex in his lab into a practical model. One challenge is selecting or developing the ideal substance to harness the bacteria’s energy. Another is cost.

But Sahin is optimistic that further research won’t take too much money—the key components used in his research are “dirt cheap,” he said. Literally.

Bacillus subtilis spores can be easily found in soil and human feces. It also happens to cause the earthy smell that comes after rainfall, a natural fragrance produced by these bacteria in response to humidity changes.

Chen said the research was the “birth of a new technological revolution.”

“It is the kind of research that often leads to major practical applications,” Peter Bower, a senior lecturer in environmental science, said in an email. “While renewable energy resources and research have grown, fossil and nuclear fuels dominate energy protection and use.”

Correction: Due to editing errors, a previous version of this article misstated Xi Chen's title as an associate computer science professor. For this project, he worked as a post-docorate research scientist. A previous version of this article also stated that some mutant forms of the bacteria had up to two times the energy density. The mutant forms actually have two orders of magnitude higher energy densities, or one hundred times more. Spectator regrets the errors.